...I bet there is a good reason to why though, and i would love to know about it as i'm a sponge when it comes to engine tech 
Benefits from longer rods on mild BBC?
- Thread starter Got Torque
- Start date
- Status
It's the rod length to stroke ratio......
On a stock 454, it's the 6.135" rod length divided by the 4.00" stroke, resulting in a 1.53:1 ratio, on a 3.760" stroke (396/427) the 6.135" rod yields a 1.63:1 ratio......
"Ideal" ratio is around 1.72:1, for the limitations we're working with, according to some engine builders.
If the pin is high enough in the piston, "rocking" is almost a non-issue, allowing a shorter skirt....less weight, less friction.
On a stock 454, it's the 6.135" rod length divided by the 4.00" stroke, resulting in a 1.53:1 ratio, on a 3.760" stroke (396/427) the 6.135" rod yields a 1.63:1 ratio......
"Ideal" ratio is around 1.72:1, for the limitations we're working with, according to some engine builders.
If the pin is high enough in the piston, "rocking" is almost a non-issue, allowing a shorter skirt....less weight, less friction.
I know how to calculate rod/stroke ratio.....but have never heard or read anything about an ideal r/s ratio. Very interesting!
I found pistons with 1,270 comp height, but that's a negative .005" and i don't like pistons poking up through the bores. Seems impossible to find any budget pistons around 1,260" height so i think i will use stock length rods and live with it :cry:
I could use .250 longer rods, but to me that's just too short of an increase to be worth it.
I found pistons with 1,270 comp height, but that's a negative .005" and i don't like pistons poking up through the bores. Seems impossible to find any budget pistons around 1,260" height so i think i will use stock length rods and live with it :cry:
I could use .250 longer rods, but to me that's just too short of an increase to be worth it.
Depending on how mild the combination is, I wouldnt think that you would see much of a benefit. If "mild" to you is 600 hp and big rpm then yeah a longer rod would be better. There are alot of options out there for a BBC.
Not to be argumentative, but Chevrolet must have thought that there is some benefit to a longer rod in a production engine, since after 40+ years of 5.7" rods the newer smallblocks have 5.94" rods.....lots of tooling got done for "no benefit".
I doubt it was because they just have extra material laying around they needed to get rid of.
I doubt it was because they just have extra material laying around they needed to get rid of.
because they changed the head design i would guess.ChrisIDV said:
Were not going to start another rod thread. I still stick with "get your crank, design your piston, connect the two together". There is no secret horspower to be found here as its a combination that makes power not a connecting rod.
I always thought the connecting rod was part of the combination? I don't see what head design has to do with deck height.
ChrisIDV said:
I guess it is because it holds the two together but on this level it really doesn't matter.
The head/port/chamber design has to do with rod length.
- Status
